Suspension Damper Having Inertia Valve and User Adjustable Pressure-Relief

ABSTRACT

A modern suspension damper, for example, a shock absorber or a suspension fork, including an inertia valve and a pressure-relief feature is disclosed. The pressure-relief feature includes a rotatable adjustment knob that allows the pressure-relief threshold to be externally adjusted by the rider “on-the-fly” and without the use of tools.

RELATED PATENTS AND APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 12/752,886, filed Apr. 1, 2010, which is a continuation of U.S.patent application Ser. No. 11/535,552, filed Sep. 27, 2006, now U.S.Pat. No. 7,699,146, which claims benefit of U.S. Provisional PatentApplication Ser. No. 60/744,128, filed Apr. 2, 2006. This application isrelated to Assignee's patent application, entitled: Bicycle Fork HavingLock-out, Blow-off, and Adjustable Blow-off Threshold, U.S. patentapplication Ser. No. 10/620,323 filed Jul. 15, 2003, now U.S. Pat. No.7,163,222, which is a continuation of Assignee's U.S. Pat. No. 6,592,136(hereinafter the '136 patent).

This application is also related to Assignee's patent applications,entitled: Inertia Valve Shock Absorber, U.S. patent application Ser. No.10/778,882, filed Feb. 13, 2004, now U.S. Pat. No. 7,128,192, andInertia Valve Shock Absorber, U.S. patent application Ser. No.11/259,629, filed Oct. 26, 2005, now U.S. Pat. No. 7,273,137, both ofwhich are children of Assignee's U.S. Pat. No. 6,581,948 (hereinafterthe '948 patent) and U.S. Pat. No. 6,604,751 (hereinafter the '751patent).

All patents and patent applications referred to herein and especiallyour earlier '136, '948, and '751 patents are incorporated by referencein their entirety in this patent application.

FIELD OF THE INVENTION

The present invention is generally related to modern suspension dampers,such as shock absorbers and suspension forks used in vehiclesuspensions. More particularly, the present invention is related to thefield of suspension dampers having an inertia valve and a useradjustable pressure-relief feature.

BACKGROUND OF THE INVENTION

Suspension forks and/or shock absorbers are often utilized on vehiclesuspensions, to absorb energy (e.g. bumps) imparted to the wheels by theterrain on which the vehicle is used. When the vehicle is a bicycle,such as a mountain bike or off-road bicycle, the use of a suspensionfork and/or shock absorber allows a rider to traverse rougher terrain,at a greater speed and with less fatigue in comparison to riding a rigidbicycle.

In our earlier '136 patent, a suspension fork having an adjustablepressure-relief valve is described. The valve can be adjusted“on-the-fly” and without the use of tools, since a control knob ispositioned external to the suspension fork for easy manipulation by theuser.

In our earlier '948 and '751 patents, rear shock absorbers andsuspension forks having an inertia valve and a pressure-relief valve aredescribed. However, in these two earlier patents, the threshold pressureat which the pressure-relief valve opens is not adjustable without adamper rebuild that involves using tools to replace the pressure-reliefshim stack in the damper with another shim stack having a differentthickness/spring rate.

Inertia valve dampers having pressure-relief features may have beensuggested in the past, see e.g. U.S. Pat. No. 1,818,141 to Lang; U.S.Pat. No. 1,873,133 to Kindl; and U.S. Pat. No. 1,953,178, also to Kindl.However, in dampers such as these, externally adjustable pressure-reliefespecially for use during the compression stroke does not appear to havebeen suggested.

Thus, there is room for improvement within the art of suspensiondampers, shock absorbers, suspension forks, and bicycle suspensions.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts an overall schematic cross-section view of a leg of asuspension fork according to a first exemplary embodiment of theinvention.

FIG. 2 depicts an enlarged cross-section of a lower portion of the forkleg depicted in FIG. 1.

FIGS. 3A and 3B depict a base valve assembly of an exemplary embodimentof the invention in first and second configurations.

FIGS. 4A and 4B depict the adjustable pressure-relief valve of anexemplary embodiment of the invention in closed and open configurations,respectively.

FIG. 5 depicts an enlarged cross-section of a lower portion of asuspension fork according to a second exemplary embodiment of theinvention.

FIG. 6 depicts a non-adjustable fluid bleed feature that may be usedwith a base valve according to the various embodiments of the invention.

FIG. 7 depicts an adjustable fluid bleed feature that may be used with abase valve according to the various embodiments of the invention.

FIG. 8 depicts an assembly view of a suspension damper, in the form of arear shock absorber having a remote reservoir, according to anotherexemplary embodiment of the invention.

FIGS. 9A and 9B depict cross-section views of the rear shock absorberand remote reservoir of FIG. 8, respectively.

DETAILED DESCRIPTION OF THE INVENTION

Prior to describing the various exemplary embodiments of the invention,it should be noted that suspension dampers according to any of thevarious exemplary embodiments described herein, while being improvementsrelative to our earlier patents ('136, '948, and '751), incorporate muchof the theory and most basic technology underlying our earlier patents.Accordingly, to maintain the clarity and conciseness of this patentapplication, where not critical to an understanding of the invention,reference should be made to our earlier '136, '948, and '751 patents,incorporated by reference herein, for a more detailed description of thevarious background technologies applicable to the invention. The presentapplication will only point out the most important similarities anddifferences between the suspension dampers of the current invention andthose of our earlier patents. Additionally, where possible, referencenumerals from the '136, '948 and '751 patents have been carried over tothe present application. Furthermore, where a technical feature appearsmore than once in a FIG, in many instances only one reference numeral isincluded to prevent clutter. Finally, a table outlining the referencenumerals used has been provided to aid cross-reference.

Suspension Forks—General Structure

The various aspects of the current invention may be implemented indifferent kinds of suspension dampers. In particular, however, thevarious aspects of the invention are especially suited forimplementation in a front suspension fork or a rear shock absorberassembly of a bicycle.

First, the invention will be described with respect to suspensiondampers in the exemplary form of front suspension forks.

FIG. 1 depicts an overall schematic cross-section view of a leg 220 of asuspension fork 10 according to a first exemplary embodiment of theinvention.

In particular, FIG. 1 depicts a compressible fork leg 220 connected to afork crown 232 (for connection to a second fork leg—not shown—and thatmay contain a spring mechanism). Fork leg 220 comprises a hollow uppertube 224 that is capable of telescopic motion in the compression andrebound directions relative to a hollow lower tube 226.

The lower tube 226 has a closed lower end and an open upper end. Theupper tube 224 is received into the lower tube 226 through its openupper end. A seal 250 is provided at the location where the upper tube224 enters the open end of the lower tube 226 and is preferablysupported by the lower tube 226 and in sealing engagement with the uppertube 224 to substantially prevent damping and/or lubrication fluid fromexiting, or a foreign material from entering, the fork leg 220.

A hydraulic damping system 240 provides a damping force in both thecompression and rebound directions to slow both compression and reboundmotions of the suspension fork by controlling the fluid flow of thedamping fluid contained within the damping system 240. In the firstexemplary embodiment, the damping system 240 is preferably an open-bath,cartridge-type damper assembly having a damping cartridge tube 252 fixedwith respect to the closed end of the lower tube 226, defining a mainfluid chamber 263, and extending vertically upward. A damper shaft 254extends vertically downward from a closed upper end of the upper tube224, through cartridge tube cap 260, and supports a piston 258 at itslower end. Thus, the piston 258 is fixed for movement with the uppertube 224 while the cartridge tube 252 is fixed for movement with thelower tube 226.

The piston 258 divides the main fluid chamber 263 of the cartridge tube252 into a first variable volume fluid chamber 262 and a second variablevolume fluid chamber 264, which may sometimes be referred to as acompression chamber (best seen in FIG. 2). The first chamber 262 ispositioned above the piston 258 and the second chamber 264 is positionedbelow the piston 258. A reservoir chamber 266 is defined between theouter surface of the cartridge tube 252 and the inner surfaces of theupper and lower tubes 224, 226. A base valve assembly 268 is positionedbetween the second chamber 264 and the reservoir chamber 266 and allowsselective fluid communication therebetween. For clarity, the details ofbase valve assembly 268 are not depicted in FIGS. 1, 2; rather thedetails of base valve assembly 268 are shown in FIGS. 3A, 3B, 4A, 4B.

Cartridge tube cap 260 includes a one-way refill valve 274 (FIG. 2),which, during inward motion of the damper shaft 254 with respect to thecartridge tube 252, allows fluid flow from the reservoir chamber 266into the first chamber 262. Thus, in an open-bath damper such as this,damping fluid flows into and out of the damping cartridge tube 252.

Cartridge tube 252 may comprise an upper cartridge portion 290 (FIG. 2)and a lower cartridge portion 292, which are threadably engaged with acartridge connector 294 to form the cartridge tube 252. Optionally, aone-piece cartridge tube may be employed. A base valve housing connector296 is fixed to the end of the lower tube 226 and supports the cartridgetube 252 on top of the base valve assembly 268 (which is located in thecartridge tube 252). The lower cartridge portion 292 of the cartridgetube 252 is preferably threadably engaged with the base valve housingconnector 296.

First Suspension Fork Embodiment—General Base Valve Assembly Structure

FIGS. 3A and 3B depict the details of a base valve assembly 268according to an exemplary embodiment of the invention.

The base valve assembly 268 according to an exemplary embodiment of theinvention may include a variety of different types of valves forregulating different aspects of fluid flow through damping mechanism240, such as, but not limited to: a compression valve 302, apressure-relief valve 400, and a lockout feature in the form of aninertia valve 306.

The compression valve 302 includes a compression piston 318 sealinglyengaged with the lower portion of the base valve housing connecter 296.The compression valve 302 is positioned in a pocket formed by base valvehousing 269 and base valve housing connector 296. As will be describedbelow, compression valve 302 controls the fluid flow of damping fluidthat has passed through an open inertia valve 306.

The compression piston 318 includes one or more compression passages 326covered by a compression shim stack 328. The compression shim stack 328is secured to the lower surface of the compression piston 318 by ashoulder 405 a of the pressure-relief chamber partition 405. Thecompression shim stack 328 may deflect about the shoulder 405 a toselectively open the compression passages 326 and place them in fluidcommunication with compression outlet passages 378 during thecompression of the suspension fork.

The inertia valve 306 is preferably somewhat similar to the inertiavalve previously described in our earlier '948 and '751 patents.Therefore, we will not provide a complete description of its structureand function at this time, since reference may be made to our otherpatents for more detail.

Generally, inertia valve 306 includes an inertia mass 362 movablebetween a closed position, where the inertia mass 362 isolates inertiainflow passage 364 a from inertia outflow passage 364 b (FIG. 3B), andan open position, where an annular recess 380 in the inertia mass 362places inertia inflow passage 364 a and inertia outflow passage 364 b influid communication with each other and inertia valve flow path 311(FIG. 3A). Inflow and outflow passages 364 a, 364 b may generallycomprise a plurality of radially aligned ports formed in the wall of themain fluid flow tube 298. Inertia valve flow path 311 is formed by aspace between main fluid flow tube 298 and pressure-relief tube 297.When the inertia valve 306 is open (FIG. 3A), fluid flow is allowedthrough annular recess 380, through inertia valve flow path 311, throughthe inertia valve fluid chamber 397, and then through the compressionpassages 326, past the shim stack 328 and into the reservoir chamber 266through compression outlet passages 378 in the base valve housing 269.When the inertia valve 306 is closed (FIG. 3B), fluid is, at leastpartially, and preferably substantially, prevented from flowing into theinertia valve flow path 311.

The inertia mass 362 is biased into its closed position (FIG. 3B) byinertia valve spring 366 (shown schematically). The inertia mass 362 ofthe current invention is preferably a solid block of high-densitymaterial, such as brass, as described in, for example, our earlier '751and '948 patents. While the inertia mass 362 of the current invention issolid as distinguished from the inertia masses of our earlier patents,which included kidney-shaped axial flow passages to provide an exit fordamping fluids displaced from the inertia valve pocket by the inertiamass (see e.g. FIGS. 4A-C of our earlier '948 patent), the currentinvention may also use the design of our earlier patents.

In the current invention, fluid displaced from the inertia valve pocket365 by the inertia mass 362 travels up a first displaced fluid gap 367,past a displaced fluid check valve 368, and up a second displaced fluidgap 369. The displaced fluid check valve 368, by allowing fluid to enterand exit the inertia valve pocket 365 only at a controlled rate,facilitates the return of the inertia mass 362 to its rest (closed)position in a predetermined and predictable time period.

Finally, the clearances of the displaced fluid check valves 368 can beimportant to the responsiveness and quick actuation of the inertia valve306. We have determined that the clearances for check valves 368 shouldbe between 0.001″-0.010″ wide and the second displaced fluid gap 369should be between 0.030″-0.200″ wide.

First Suspension Fork Embodiment—Basic Pressure Relief

The suspension fork according to the invention is provided with apressure-relief feature. The pressure-relief feature may comprise apressure-relief valve 400. The pressure-relief valve 400, which maysometimes be referred to as a blowoff valve, is positioned below thepressure-relief chamber partition 405, and shown in more detail in FIGS.4A and 4B (although the full details and description of the blow-offvalve's operation may be found in our earlier '136 patent). Thecompression valve 302 and the pressure-relief valve 400 are fluidicallyisolated from one another by the pressure-relief chamber partition 405.A pressure-relief chamber 308 is defined between base valve housing 269and pressure-relief chamber partition 405.

Pressure-relief chamber 308 is in open and unrestricted fluidcommunication with compression chamber 264 (see FIG. 3A). Fluidcommunication is achieved by a fluid passageway 407 in thepressure-relief chamber partition 405 that accesses a fluid passageway297 a through pressure-relief tube 297, which itself is positionedwithin main fluid flow tube 298. Funnel 299 may be used for directingthe fluid from compression chamber 264 into main fluid flow passageway298 a and fluid passageway 297 a.

When the fluid pressure of the damping fluid within the pressure-reliefchamber 308 has not achieved a threshold value sufficient to overcomethe pre-load of pressure-relief spring 448, pressure-relief piston 446does not move relative to the pressure-relief inlet 444 and fluid flowfrom the pressure-relief chamber 308 to reservoir chamber 266 issubstantially prevented (FIG. 4A).

When the fluid pressure of the damping fluid within the pressure-reliefchamber 308 achieves a threshold value sufficient to overcome thepre-load of pressure-relief spring 448, pressure-relief piston 446 willmove relative to the pressure-relief inlet 444 and fluid flow from thepressure-relief chamber 308 to reservoir chamber 266 throughpressure-relief outlets 454 is allowed (FIG. 4B).

First Suspension Fork Embodiment—Basic Operation

Having described the basic structure of a suspension fork 10 and a basevalve assembly 268 according to an exemplary embodiment of theinvention, their basic operation will now be described.

When the front wheel (not shown) of a bicycle (not shown) encounters abump, as is generally known to those skilled in the art, a force isexerted on the suspension fork 10 that tends to compress the fork tubes224, 226 in relation to each other by upwardly accelerating lower forktube 226. If the upward acceleration of the lower fork tube 226 alongits longitudinal axis (which is the same as the axis of travel of theinertia mass 362) is below a predetermined threshold defined by thepre-load on inertia valve spring 366, the inertia mass 362 will not moveand remains in its closed position, preventing fluid flow through theannular recess 380 and into inertia valve flow path 311 (FIG. 3B).Increased pressure within the compression chamber 264 due to the forceexerted on the suspension fork 10 is communicated through the main fluidflow passageway 298 a, fluid passages 297 a and 407 and into thepressure-relief chamber 308.

If the fluid pressure within the pressure-relief chamber 308 has notachieved the threshold value needed to overcome the pre-load ofpressure-relief spring 448, the pressure-relief valve 400 remainsclosed, substantially preventing fluid flow. Therefore, the suspensionfork 10 remains substantially rigid because most fluid flow has beenprevented (i.e., only movement resulting from a fluid bleed, clearanceleakage, or fluid compressibility may occur). This is shown in FIG. 4A,where the compression flow does not continue past the pressure reliefchamber 308. Under these conditions, the damping cartridge 252 andsuspension fork 10 are referred to as being “locked out”.

The pressure-relief valve 400 selectively allows fluid flow from thecompression chamber 264 to the reservoir 266 at high compressive fluidpressures or shaft speeds. Preferably, the pressure-relief valve 400remains closed at low and mid-compressive fluid pressures or shaftspeeds. Advantageously, “lock out” of the suspension fork 10 preventsrider pedal energy from being absorbed by the suspension fork 10 therebyallowing such energy to instead promote forward motion of the bicycle.If a large bump is encountered, such that the pressure within thecompression chamber 264 rises above the threshold necessary to open thepressure-relief valve 400, the valve 400 operates to allow fluid flowfrom the compression chamber 264 to the reservoir 266. Advantageously,this prevents damage to the various seals of the suspension fork 10 andprevents the entire force of the bump from being transferred to therider.

If the fluid pressure within the pressure-relief chamber 308 due to thefluid flow of damping fluid into pressure-relief chamber 308 achievesthe threshold pressure needed to overcome the pre-load ofpressure-relief spring 448, the pressure-relief valve 400 will open toallow fluid to flow into the reservoir chamber 266 through thepressure-relief outlets 454. Thus, the suspension fork 10 is able tocompress and its compression damping rate is determined primarily by thespring rate of pressure-relief spring 448 of the pressure-relief valve400 and the diameter of pressure-relief inlet 444. This is referred toas “blowoff”. This use of the term “blowoff” should not be confused withthe less common usage, such as in U.S. Pat. No. 6,120,049 (“blowoff” isused in the context of rebound refill check valves).

When the upward acceleration of the lower fork leg 226 exceeds apredetermined threshold, the inertia mass 362 overcomes the biasingforce of the inertia valve spring 366 and moves into a position thatplaces the passages 364 a and 364 b into fluid communication with eachother via annular recess 380 and fluid flow is allowed into the inertiavalve flow path 311 formed by a space between main fluid flow tube 298and pressure-relief tube 297. This flow proceeds through the inertiavalve fluid chamber 397 and then through the compression passages 326,past the shim stack 328 and into the reservoir chamber 266 throughcompression outlet passages 378 in the base valve housing 269, asillustrated in FIG. 3A. Accordingly, at pressures lower than thepredetermined pressure-relief pressure, when the inertia mass 362 isopen (down), fluid is permitted to flow from the compression chamber 264to the reservoir chamber 266 and the suspension fork 10 is able tocompress. The compression damping rate is determined primarily by thespring rate of the compression shim stack 328. Under these conditions,the damping cartridge 252 and suspension fork 10 are referred to asbeing not “locked out”.

First Suspension Fork Embodiment—Adjustable Pressure-Relief

In some prior inertia valve suspension forks, such as those described inour earlier '751 and '948 patents, pressure-relief was achieved using apressure-relief shim stack for controlling the fluid flow between whatis called a blowoff chamber, the separator chamber, and the reservoir(see FIG. 17 and associated text in our earlier '751 and '948 patents).In these prior designs, there is no capability to externally (andespecially “on-the-fly”) adjust the threshold pressure because thepressure-relief feature was contained entirely inside the suspensiondamper. Therefore, the threshold pressure could only be changed bytaking the suspension fork and cartridge apart and replacing thepressure-relief shim stack with another shim stack having a differentthickness/spring rate. This process was not conducive to theoperator/rider selecting and/or adjusting the threshold pressure on anyregular basis and especially “on-the-fly” (e.g. during the course of aride) and without the use of tools.

However, as described in our earlier '136 patent, it is often preferablefor the operator/rider to have the ability to select and/or adjust thethreshold pressure on a regular basis. Therefore, an ability to adjustthe threshold pressure “on-the-fly”, in the sense of “on the trail” andwithout the use of tools was proposed.

Accordingly, the suspension fork 10 according to the current inventionhas been provided with a pressure-relief feature in the form of anadjustable pressure-relief valve 400 having portions positioned insideand outside the suspension fork. As previously mentioned, adjustablepressure-relief valve 400 may be very similar to the valve described asa blowoff valve in our earlier '136 patent and therefore we will notprovide a complete description of its structure and function at thistime, since reference may be made to our earlier '136 patent.

However, generally, a rotatable pressure-relief adjustment knob 432,positioned outside of the suspension fork provides the capability ofeasily adjusting the threshold pressure.

In particular, knob 432 is attached to support shaft 462. Therefore,rotation of knob 432 causes the rotation of the support shaft 462.Furthermore, through threads in lower tube and support shaft 462,rotation of support shaft 462 is converted to axial movement of thesupport shaft 462 relative to the base valve assembly 268. This axialmovement of the support shaft 462 changes the compressed or pre-loadedlength of the portions of the pressure-relief feature positioned withinthe suspension fork, such as pressure-relief spring 448, and therebyvaries the pre-load on the pressure-relief spring 448. The pre-load ofthe pressure-relief spring 448 influences the threshold pressure withinthe pressure-relief chamber 308 that is necessary to open thepressure-relief valve 400. More pre-load raises the threshold pressure,while less pre-load decreases the threshold pressure.

Thus, pressure-relief threshold adjustment knob 432, positioned externalto the cartridge tube 252, the suspension fork leg 220, and tubes 224,226, allows for the operator/rider to have the ability to select and/oradjust the threshold pressure on a regular basis and especially“on-the-fly”, in the sense of “on the trail” and without the use oftools was proposed.

Second Suspension Fork Embodiment—Closed Damper

FIG. 5 depicts an enlarged cross-section of a lower portion of asuspension damper according to a second exemplary embodiment of theinvention. This exemplary embodiment is similar to the first exemplaryembodiment in that it comprises a suspension fork with a dampingmechanism 240′ that includes a base valve assembly 268′ having an:inertia valve 306; a compression valve 302 and an adjustablepressure-relief valve 400. What differentiates the second exemplaryembodiment from the first exemplary embodiment are: the complete sealingof cartridge tube 252, the inclusion of a fluid biasing element (forexample, in the form of a bladder), and the elimination of reservoirchamber 266. These differences convert the open-bath damper of the firstexemplary embodiment into the closed damper of the second exemplaryembodiment. Benefits of closed dampers over open-bath dampers are:decreased amount of damping fluid needed to operate the dampingmechanism and less chance for the damping fluid to become aerated.Aeration tends to degrade the performance of damping fluid (i.e.,degrades its incompressibility) and results in an effect sometimesreferred to as “lockout lag”.

As shown in FIG. 5, the differences between the first exemplaryembodiment and the second exemplary embodiment generally begin in thearea of base valve housing connector 296′. In this second exemplaryembodiment, base valve housing connector 296′ has been made unitary withthe compression piston. Therefore, base valve housing connector 296′ hascompression passages 326′ (in fluidic communication with the inertiavalve flow path 311) selectively blocked by compression shim stack 328.Similarly, base valve housing connector 296′ has first and secondrebound passages 409, 410 and rebound check plate 411, loaded by reboundspring 412, for controlling rebound flow through second rebound passage410.

Base valve housing 269 of the first exemplary embodiment is now replacedwith cartridge bottom 510 that is connected to base valve housingconnector 296′ via extension cylinder 511. A portion of the inner volumebound by the extension cylinder 511 defines an internal fluid reservoir512. Additionally, within extension cylinder 511 is a fluid biasingelement, preferably in the form of a bladder 520, a well-known componentin damping technology, and that may be made of any known flexible, fluidresistant, and resilient material. The bladder 520 preferably has anannular shape defining an open center portion 521. Support shaft 462′can extend through the open center portion 521 from the general area ofthe pressure-relief piston 446′ and pressure-relief spring 448′ to, andexternal of, cartridge bottom 510. This annular bladder 520 is describedin more detail in our co-pending application entitled “Damping Cylinderwith Annular Bladder”, U.S. patent application Ser. No. 11/291,058,filed on Nov. 29, 2005, and incorporated by reference herein.

As is known in the art, bladder 520 acts in a manner similar to otherfluid biasing elements, such as gas or coil spring-backed internalfloating pistons (“IFPs”) to keep the damping fluid in the internalfluid reservoir 512 under pressure as the damping fluid exits and entersinternal fluid reservoir 512 and keep the gas within bladder 512 and thedamping fluid separate.

Having described the basic structure of a suspension fork 10 accordingto this second exemplary embodiment of the invention and in the form ofa closed damper that does not allow fluid to flow into and out of thedamping cartridge 252, its basic operation will now be described.

a) Inertia Valve Closed—Fluid flows down fluid passage 297 a, throughpressure-relief inlet 444 and into contact with pressure-relief piston446′. If the fluid threshold pressure is reached, the fluid pressure onpressure-relief piston 446′ will overcome the pre-load ofpressure-relief spring 448′ and cause pressure-relief piston 446′ todescend and open, and fluid flow into reservoir 512 through passage 409is allowed. If the threshold pressure is not reached, the fluid pressureon pressure-relief piston 446 will not overcome the pre-load ofpressure-relief spring 448′, pressure-relief piston 446′ will remainclosed, and fluid flow into internal fluid reservoir 512 through passage409 will be substantially prevented. Therefore, tubes 224, 226 will notbe capable of substantial relative movement and the suspension fork 10will remain substantially rigid.

b) Inertia Valve Open—Fluid flows down inertia valve flow path 311,through inertia valve fluid chamber 397, and into compression passages326′. The fluid pressure on the fluid will overcome the spring force ofcompression shim stack 328 and fluid will flow into internal fluidreservoir 512 providing the fork the ability to compress.

c) Rebound—As tubes 224, 226 extend apart and the fluid pressuredecreases in compression chamber 264, fluid will flow from the internalfluid reservoir 512 back to the compression chamber 264. This reboundflow will travel up passages 409 and 410 and overcome the bias onrebound spring 412, deflect rebound plate 411 and allow the fluid flowto continue up passage 297′ and back into the compression chamber 264.

Thus, with the second exemplary suspension fork embodiment, there is nocirculation of fluid outside of cartridge tube 252 during the operationof the damping mechanism 240′. This reduces the opportunity for thefluid to become aerated and have its performance degraded. In otherwords, while the first exemplary embodiment has a cartridge tube 252that was substantially sealed (i.e., fluid normally contained within thecartridge but can enter and leave the cartridge during rebound andcompression, respectively), the second exemplary embodiment has acartridge tube 252 that is completely sealed (i.e., fluid cannot enterand leave the cartridge absent deconstruction or rupturing of cartridgetube 252).

Fluid Bleed—In General

A fluid bleed feature can be incorporated into any of the suspensiondampers according to the various exemplary embodiments of the invention.An example of a fluid bleed is shown in FIG. 6, which is a modificationof the exemplary embodiment of FIG. 5.

In FIG. 6, pressure-relief piston 446″ is not solid as depicted in otherfigures herein, but includes a bleed inlet passage 517 and a bleedoutlet passage 519, having an exemplary diameter of 0″-0.012″ thatprovides at least one alternative fluid path between fluid passage 297 aand internal fluid reservoir 512 to allow for a bleed flow Q. Thesebleed passages 517, 519 provide for only low speed fluid flows becauseat higher speeds, the resulting fluid pressures open the pressure-relieffeature. An exemplary purpose for having this low-speed fluid bleed pathis to provide a means by which when a rider mounts their bicycle (notshown) and places the initial load (i.e., their body weight) on thesuspension fork, the suspension fork can slowly compress to its loadedposition (“sag”). Note that in a suspension fork having a bleed, evenwhen the suspension fork is in a position that sometimes may be referredto as locked out (either manually or by use of an inertia valve), duringvery low speed compression the suspension fork retains at least somedegree of compressibility (regardless of whether the fluidpressure-relief valve has opened). Therefore, under such conditions thefork is not, nor would it be considered, “completely rigid”.

Fluid Bleed—Adjustable

The fluid bleed feature may also be manually adjustable.

An exemplary embodiment of a manually adjustable fluid bleed feature isshown in FIG. 7. Pressure-relief spring 448″ is maintained betweenpressure-relief piston 446″ and the upper surface 462 a of shaft 462.Support shaft 462 is now provided with a tapered bleed needle 525 at itsupper end. Thus, as shaft 462 axially moves as it is rotated by turningknob 432, bleed needle 525 will move towards or away from bleed inlet517 in pressure-relief piston 446″ (which is biased againstpressure-relief inlet 444) to vary the size of the bleed path while alsovarying the pre-load on pressure-relief spring 448″.

Adjustable bleed allows a rider to control the rate at which the fluidmay pass through the fixed-radius bleed inlet 517 and hence the abilityof the suspension fork to sag or compensate for very low speedcompression flows.

Rear Shock Absorber

FIG. 8 depicts an assembly view of a suspension damper 30 according toanother exemplary embodiment of the invention, in the form of acompressible rear shock absorber 38 having a remote reservoir 44. FIG.9A depicts a cross-section view of the rear shock absorber 38. FIG. 9Bdepicts a cross-section view of remote reservoir 44, which contains aninertia valve 138. While rear shock absorber 38 is shown herein asfluidically connected to remote reservoir 44 by hose 46, it is alsopossible for reservoir 44 to be a piggyback reservoir, as known in theart. The operation of suspension dampers such as these is described ingreat detail in our earlier '751 and '948 patents.

The current exemplary embodiment of the invention provides these typesof suspension dampers with an externally adjustable pressure-relieffeature.

According to this exemplary embodiment of the current invention, asshown in FIG. 9B, reservoir 44 comprises a reservoir tube 122 containingan inertia valve 138. Within reservoir tube 122, a portion of theadjustable pressure-relief feature is provided in the exemplary form ofa pressure-relief port 540 and a pressure-relief valve 541.Pressure-relief port 540 may be located in fastener 168. When open,pressure-relief port 540 provides an additional fluid flow circuitbetween blowoff chamber 170 and reservoir chamber 128 (i.e., in additionto blowoff valve 140). Pressure-relief valve 541 comprises apressure-relief valve element 545, having a shaft portion 546 and a headportion 547, is mounted for longitudinal movement in a pressure-reliefbore 548 in control shaft 549, and biased by spring 550 towards aposition that blocks pressure-relief port 540. Control shaft 549 isattached to an adjuster, positioned outside of the suspension damper,for example, a rotatable adjustment knob 551, in any conventional mannerthat, depending upon the direction in which knob 551 is turned, controlshaft 549 moves either towards or away from the blowoff valve 140.Accordingly, depending upon the direction in which knob 551 is turned,the pre-load on spring 550 increases or decreases. As with otherembodiments of the invention described herein, the pre-load of spring550 influences the threshold fluid pressure within the blowoff chamber170 that is necessary to open the pressure-relief valve 541. Morepre-load raises the threshold pressure, while less pre-load decreasesthe threshold pressure. The pre-load created by spring 550 will neverexceed the spring force/pressure needed to open blowoff valve 140.Therefore, by the user rotating knob 551, the user can manually adjustthe threshold pressure.

The blowoff valve 140 is primarily comprised of a cylindrical base and ablowoff cap. The upper end of the base is open and includes a threadedcounterbore. The blowoff cap is includes a threaded outer surfaceengaging the threaded counterbore. A threaded fastener 168 fixes a valveseat of the pressure relief valve 541 to the blowoff cap. A lower end ofthe base is threaded and engages a threaded upper end of the reservoirshaft 134. A floating piston is disposed in the reservoir chamber 128and isolates gas from the damping fluid. The control shaft 549 extendsthrough the floating piston.

Having described the basic structure of a suspension damper 30 accordingto this exemplary embodiment of the invention and in the form of a rearshock absorber 38 having a remote reservoir 44, its basic operation willnow be described.

When suspension damper 30 is subjected to a bump-induced compressionthat is not of a magnitude or direction that causes inertia valve 138 toopen, fluid pressure in central passage 136 of reservoir shaft 134 iscommunicated to blowoff chamber 170. When the fluid pressure in blowoffchamber 170 is greater than or equal to the threshold pressure requiredto overcome the pre-load of spring 550, pressure-relief valve 541 willopen and fluid will flow from blowoff chamber 170 to reservoir chamber128 through pressure-relief port 540. This fluid flow allows the shockabsorber to compress.

When shock absorber 38 is subjected to a large bump-induced compressionthat is still not of a magnitude or direction that causes inertia valve138 to open, the fluid flow through central passage 136 of reservoirshaft 134 greatly increases the fluid pressure within blowoff chamber170. Despite the fact that pressure-relief valve 541 will open and allowsome fluid flow through pressure-relief port 540, if the fluid pressurewithin blowoff chamber 170 achieves a high enough value, the thresholdpressure of blowoff valve 140 will be overcome and fluid will flow fromthe blowoff chamber 170 to the reservoir chamber 128 via the blowoffvalve 140.

Thus, using knob 551, positioned outside of the shock absorber 38 andthe reservoir 44, the operator/rider will have the ability to selectand/or adjust the threshold pressure on a regular basis and especially“on-the-fly” (e.g. during the course of a ride) and without the use oftools.

Conclusion

Though the invention has been described with respect to certainexemplary embodiments, the scope of the invention is solely limited bythe scope of the appended claims.

Reference Numerals Used In This Application  10 suspension fork(suspension damper)  30 suspension damper (shock absorber/reservoir)  38rear shock absorber  44 remote reservoir  46 hose 122 reservoir tube 128reservoir chamber 134 reservoir shaft 136 central passage 138 inertiavalve assembly (remote reservoir) 140 blowoff valve 168 fastener 170blowoff chamber 220 fork leg 224 upper tube 226 lower tube 232 crown 240damping system 250 seal 252 damping cartridge tube 254 damper shaft 258piston 260 tube cap 262 first variable volume fluid chamber 263 mainfluid chamber 264 second variable volume fluid chamber/compressionchamber 266 reservoir chamber 268 base valve assembly 269 base valvehousing 274 refill valve 290 upper cartridge portion 292 lower cartridgeportion 294 cartridge connector 296 base valve housing connector 297pressure-relief flow tube 297a fluid passageway 298 main fluid flow tube298a main fluid flow passage 299 funnel 302 compression valve 306inertia valve 308 pressure-relief chamber 311 inertia valve flow path3]8 compression piston 326 compression passages 328 compression shimstack 362 inertia mass 364a inertia inflow passage 364b inertia outflowpassage 365 inertia valve pocket 366 spring 367 first displaced fluidgap 368 displaced fluid check valve 369 second displaced fluid gap 378compression outlet passages 380 annular recess 397 inertia valve fluidchamber 400 pressure-relief valve 405 pressure-relief chamber partition405a pressure-relief chamber partition shoulder 407 fluid passageway 409first rebound passage 410 second rebound passage 411 rebound check plate412 rebound spring 432 knob 444 pressure-relief inlet 446pressure-relief piston 448 pressure-relief spring 454 pressure-reliefoutlet 462 support shaft 462 shaft portion 462a stationary surface 510cartridge bottom 511 extension cylinder 512 internal fluid reservoir 517bleed inlet 519 bleed outlet 520 bladder 521 open center portion (ofbladder) 525 bleed needle 540 pressure relief port 541 pressure-reliefvalve 545 pressure-relief valve element 546 pressure-relief valve shaftportion 547 pressure-relief valve head portion 548 pressure-relief bore549 control shaft 550 spring 551 knob

1. A suspension damper operable between a compressed position and anextended position, comprising: a compression chamber having a volumereducing in response to operation of the suspension damper from theextended position to the compressed position; a rebound chamber having avolume reducing in response to operation of the suspension damper fromthe compressed position to the extended position; a reservoir chamberfor receiving fluid from the compression chamber via a first fluid path,a second fluid path, and a third fluid path; an inertia valve having aninertia mass slideably moveable relative to the first fluid path, theinertia mass at least substantially closing the first fluid path when ina closed position and movable to an open position in response toacceleration of at least a portion of the suspension damper; a blowoffvalve at least substantially closing the second fluid path when in aclosed position and movable to an open position in response to pressurein the compression chamber equaling or exceeding a first pressurethreshold; and a pressure relief valve at least substantially closingthe third fluid path when in a closed position and movable to an openposition in response to pressure in the compression chamber equaling orexceeding an adjustable second pressure threshold.
 2. The suspensiondamper of claim 1, further comprising a biasing member for biasing atleast one of the inertia valve, the blowoff valve, and the pressurerelieve valve are biased into the closed position.
 3. The suspensiondamper of claim 1, wherein the first pressure threshold is greater thanthe second pressure threshold such that the pressure relief valve ismovable to the open position before the blowoff valve moves to the openposition.
 4. The suspension damper of claim 1, wherein the firstpressure threshold is equal to the second pressure threshold.
 5. Thesuspension damper of claim 1, further comprising a controller operableto adjust the second pressure threshold of the pressure relief valve. 6.The suspension damper of claim 5, wherein the pressure relief valvecomprises a valve element biased by a biasing member into the closedposition to close fluid flow through the third fluid path.
 7. Thesuspension damper of claim 6, wherein the controller is operable toincrease or decrease pre-load of the biasing member on the valve elementto adjust the second pressure threshold of the pressure relief valve. 8.The suspension damper of claim 7, wherein the controller comprises aknob coupled to a shaft that supports the biasing member, and whereinrotation of the knob moves the shaft axially to increase or decrease thepre-load of the biasing member on the valve element.
 9. The suspensiondamper of claim 8, further comprising a floating piston disposed in thereservoir chamber and configured to separate a gas from liquid disposedin the reservoir chamber, wherein the shaft extends through the floatingpiston.
 10. The suspension damper of claim 1, wherein the pressurerelief valve is in fluid communication with a chamber of the blowoffvalve such that pressure within the chamber exceeding the secondthreshold opens the pressure relief valve.
 11. The suspension damper ofclaim 10, wherein pressure within the chamber exceeding the firstthreshold opens the blowoff valve and the pressure relief valve.
 12. Thesuspension damper of claim 1, wherein the acceleration of the portion ofthe suspension damper is caused when the suspension damper moves fromthe extended position to the compressed position.
 13. The suspensiondamper of claim 1, wherein the inertia valve comprises: an outer flowtube having first and second flow ports formed through a wall thereof;an inner flow tube disposed within the outer flow tube so that anannulus is formed therebetween and having a head isolating the firstflow port from the annulus; the inertia mass made from a high densitymaterial, having a recess formed therein, and movable between the openand closed positions, wherein the recess provides fluid communicationbetween the first and second flow ports in the open position; a springbiasing the inertia mass toward the closed position; a pocket receivingthe inertia mass in the open position; and a check valve allowing flowfrom the pocket and obstructing flow into the pocket.
 14. The suspensiondamper of claim 1, wherein the reservoir chamber is externally coupledto the compression and rebound chambers.
 15. A suspension damperoperable between a compressed position and an extended position,comprising: a damper body defining a compression chamber and a reboundchamber; a reservoir body defining a reservoir chamber for receivingfluid from the compression chamber via a first fluid path, a secondfluid path, and a third fluid path; an inertia valve having an inertiamass slideably movable relative to the first fluid path to open andclose fluid communication between the first fluid path and the reservoirchamber, wherein the inertia mass is movable in response to accelerationof at least a portion of the suspension damper; a blowoff valve operableto open and close fluid communication between the second fluid path andthe reservoir chamber, wherein the blowoff valve includes a chamber influid communication with the first fluid path; and a pressure reliefvalve operable to open and close fluid communication between the thirdfluid path and the reservoir chamber, wherein the pressure relief valveis coupled to the blowoff valve such that pressure in the chamber of theblowoff valve operates the pressure relief valve.
 16. The suspensiondamper of claim 15, wherein the pressure relief valve comprises a valveelement biased by a biasing member into a closed position to close fluidflow through the third fluid path.
 17. The suspension damper of claim16, further comprising a controller operable to increase or decreasepre-load of the biasing member on the valve element to adjust a pressurethreshold required to open the pressure relief valve.
 18. The suspensiondamper of claim 17, wherein the controller comprises a knob coupled to ashaft that supports the biasing member, and wherein rotation of the knobmoves the shaft axially to increase or decrease the pre-load of thebiasing member on the valve element.
 19. The suspension damper of claim15, wherein the reservoir body and the damper body are externallypositioned relative to the each other.